Heat treating apparatus

ABSTRACT

An apparatus for simultaneously treating platelike workpieces with heat and pressure comprises a hearth in which a table means and a cover member define a chamber provided with heating means. The hearth is equipped with means for generating a ram pressure and besides with special means for ensuring that workpieces put on the table means and forming thereon stacks of different heights will be affected by substantially equal ram pressure acting from below of the movably mounted table means.

United States Patent [191 Huttermann [4 1 Feb. 18,1975

1 1 HEAT TREATING APPARATUS Inventor: Bernhard Huttermann,Glinde,

Germany [73] Assignee: Jurid Werke GmbH, Glinde,

Germany [22] Filed: Oct. 1, 1973 [21] Appl. No: 402,046

[30] Foreign Application Priority Data [5 6] References Cited UNITED STATES PATENTS 177,487 5/1876 Field 34/144 508,112 11/1893 Miller 1,734,901 11/1929 Gerrie 34/143 2,454,253 11/1948 Kriveton 432/6 2,671,160 3/1954 Segsworth 432/ 3,456,581 7/1969 Zuber 34/144 FOREIGN PATENTS OR APPLICATIONS 861,584 10/1940 France 432/125 Primary ExaminerJ0hn J. Camby Assistant Examiner-Henry C. Yuen Attorney, Agent, or Firm-Roylance, Abrams, Berko & Kaul [57] ABSTRACT An apparatus for simultaneously treating platelike workpieces with heat and pressure comprises a hearth in which a table means and a cover member define a chamber provided with heating means. The hearth is equipped with means for generating a ram pressure and besides with special means for ensuring that work pieces put on the table means and forming thereon stacks of different heights will be affected by substantially equal ram pressure acting from below of the movably mounted table means.

5 Claims, 5 Drawing Figures 1,549,823 8/1925 White 432/121 4 f l I/ 27 PATENTED 8975 3.867. 093

SHEET? 0F 2 HEAT TREATING APPARATUS BACKGROUND OF THE INVENTION The invention relates to apparatus for heat treating machine parts of substantially platelike form with simultaneous application of ram pressure.

Apparatus of such a kind is frequently used for sintered powder-metallurgically prepared plates for clutches or brakes, ram pressure being appliedto the stacked parts during the heat treatment for sintering the friction lining material to the backing plates.

Conventional apparatus comprises a hearth providing a surface for the reception of the material that is to be treated, a vault covering the hearth to which it is anchored and being provided with heating means, the pressure being generated by the hearth surface and/or the vault being mechanically or hydraulically moved closer together. Usually a hoodwhich stands in an oil trough forming a seal is provided between the hearth and the vault to enable sintering to proceed in a protective gas atmosphere.

The size of the plates that are to be sintered is within a diameter of 1000 mm, but plates of a diameter exceeding 500 mm are too rare to justify the installation of pressure sintering furnaces having hearths of appropriate size merely for dealing with these larger sized plates only. Therefore loarger sized furnaces are used also for simultaneously sintering several stacks of smaller diameter plates. In order to prevent the application of pressure to be too unevenly divided preferably no more than three stacks of parts are treated in one furnace at the same time.

However, due to unavoidable manufacturing toleratious, such platelike workpieces show differences in thickness caused by the production steps which procede the sintering process. Therefore, when more than one stack of plates are introduced into a pressure sintering Furnace, the stacks composed of equal numbers of pieces, will show different heights even if the design size of all the plates is the same. These differences are not easy to compensate even by the insertion of packing pieces. Stacks of unequal heights result in the application of unequal pressure .to the several stacks and hence to the workpieces. The uniform application of that pressure which is needed for complete sintering of the linings to the backing, or carrier plates therefore cannot be ensured. Consequently the simultaneous treatment of several stacks in the hitherto conventional manner leads to high rates of the rejects and rquires the destruction of a greater number of samples than is otherwise usual for testing whether sintering has been complete.

OBJECTS AND SUMMARY OF THE INVENTION It is therefore an object of the present invention to eliminate these drawbacks and to provide a heat treating apparatus that will permit stacks of different heights to be satisfactorily and economically treated.

According to the invention this is achieved in apparatus of the specified kind by dividing the hearth surface into component surfaces which are independently movable by associated members of the pressure generating means.

A useful embodiment of the proposed heat treating apparatus also comprises coupling means which permit individual component surfaces of the hearth to be moved jointly with one or more or all of the others.

This proposal enables parts that are to be sintered to be arranged in stacks of different heights on the several component surfaces of the hearth and each to be subjected to controllable pressure independently of the others, or alternatively several or all the component surfaces can be used jointly in combination should this be desired.

Moreover, if desired, only part of the furnace chamber need be filled and the treatment performed under ideal pressure conditions although in such a case the total capacity is only fractionally utilised. On the other hand, if the pressure conditions resulting from an application of pressure to three stacks in the formerly conventional manner is considered acceptable, then the capacity of such apparatus can be increased to several times that of conventional equipment.

Further objects and advantages are to be derived from the claims, from the following particular descrip tion and from the drawings which schematically exemplify heat treatment equipment according to the invention in a pressure sintering furnace.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conventional pressure sintering furnace.

FIG. 2 is a pressure sintering furnace according to the invention,

FIG. 3 is a view from above of the hearth of a furnace according to the invention,

FIG. 4 is a side elevation of the component parts of a hearth and of a coupling means in a furnace according to the invention, and

FIG. 5 is a view of the arrangement in FIG. 4, seen in plan.

DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 is a representation of a conventional pressure sintering furnace comprising a hearth 11 supporting a hearth plate 12 under a vault 13 which can be anchored to the hearth, and which is equipped with heating means 14. The hearth plate 12 carries several stacks 16 of maching parts that are to be sintered. The stacks are enclosed within a protective hood 17, an immersion oil seal 18 preventing the ambient atmosphere from gaining access. The hearth plate 12 can be forced by a pressure generating means 15, such as a hydraulic cylinder and piston, to move towards the roof of the vault 13 and to compress the stacks 16.

FIG. 23 is a hearth 21 and a furnace vault 22 equipped with heating means 23. Accoding to the invention the supporting surface on the hearth 21 (refer also top FIG. 3) comprises several hearth plates 241, 242, 243, 244. The hearth plates 241 to 244 are each independently movable by a separate hydraulic pressure generator 251. A hood 27 for a protective gas and an oil seal 28 are also provided.

It will be understood from FIG. 3 that the hearth plates 241, 242, 243, 244 in one embodiment of the proposed equipment are quadrants of a circle. However, for treating parts that have different kinds of contours the hearth surface may also be divided in other ways and the component plates may have alternative geometrical shapes, for example squares or rectangles.

If necessary stacks 261 of varying initial heights can be trated in equipment according to the invention by the interposition of packing members 262 for equalising the heights of the stacks 261.

FIGS. 4 and 5 demonstrate how the component plates of the hearth can be coupled together by coupling means 245 when the machine parts 263 which project beyond the contours of an individual component hearth plate are to be treated. For coupling several of the hearth plates together so that they can be used as one plate they are covered with a coupling plate 245 which rigidly joins them together. Fins 246 which project from the coupling plate fit into the clearance gaps between the component plates and ensure not only that the coupling plate 245 will be reliably located, but also that the rigidity of the plate and the rigidity of the coupling will be improved.

The weight of the parts 263 forming a stack, as indicated at 261 plus that of the coupling plate 245 is sufficient to prevent unequal movements of the several component hearth plates due to differential frictional resistance in the pressure generating units 251.

Moreover, such coupling plates provide a flat unbroken surface which prevents the workpieces at the bottom of the stacks from being damaged.

What is claimed is:

1. An apparatus for simultaneously treating substantially plate-shaped workpieces with heat and pressure comprising:

a hearth having surface means for the reception of workpieces to be treated, and cover means defining together with said surface means a treatment chamber;

said cover means having a portion extending substantially in parallel to, but spaced apart from said surface means;

heat generating means within said chamber;

ram means in cooperating relation with said surface means for moving said surface means under pressure in a'direction towards said portion of said cover means and into said chamber to press the workpieces thereon against said cover means;

said surface means comprising a plurality of component surfaces and said ram means having an equal plurality of ram members;

each of said component surfaces being mounted in said hearth for independent movement by an associated one of said ram members; and

coupling means for releasably interconnecting at least two component surfaces of said plurality of component surfaces, said interconnected component surfaces being uniformly movable by their associated members.

2. An apparatus according to claim 1, characterized in that said component surfaces are separated the one form the other by small gaps, and in that said coupling means is a plate having fins which exactly fit into the gaps between said component surfaces to be coupled.

3. An apparatus according to claim 1, characterized in that said component surfaces define means for receiving portions of said coupling means and in that said coupling means is a plate having portions received by said means for receiving.

4. In an apparatus for simultaneously treating substantially plate-shaped workpieces with heat and pressure having a hearth having surface means for the reception of workpieces to be treated and cover means defining together with said surface means a treatment chamber, said cover means having a portion extending substantially in parallel to, but spaced apart from said surface means; heat generating means within said chamber; ram means in cooperating relation with said surface means for moving said surface means under pressure in a direction toward said portion of said cover means into said chamber to press the workpieces thereon against said cover means, the improvement comprising:

a plurality of separate component surfaces comprising said surface means,

a plurality of ram members comprising said ram means,

each of said component surfaces being mounted in said hearth for independent movement by an associated one of said ram members, and

said cover means including packing means, located above at least one of said component surfaces, for reducing the dimension of the treatment chamber in the direction of the movement of said surface means.

5. An apparatus according to claim 4, characterized in that each of said component surfaces is larger than the bottom surface of each workpiece. 

1. An apparatus for simultaneously treating substantially plateshaped workpieces with heat and pressure comprising: a hearth having surface means for the reception of workpieces to be treated, and cover means defining together with said surface means a treatment chamber; said cover means having a portion extending substantially in parallel to, but spaced apart from said surface means; heat generating means within said chamber; ram means in cooperating relation with said surface means for moving said surface means under pressure in a direction towards said portion of said cover means and into said chamber to press the workpieces thereon against said cover means; said surface means comprising a plurality of component surfaces and said ram means having an equal plurality of ram members; each of said component surfaces being mounted in said hearth for independent movement by an associated one of said ram members; and coupling means for releasably interconnecting at least two component surfaces of said plurality of component surfaces, said interconnected component surfaces being uniformly movable by their associated members.
 2. An apparatus according to claim 1, characterized in that said component surfaces are separated the one form the other by small gaps, and in that said coupling means is a plate having fins which exactly fit into the gaps between said component surfaces to be coupled.
 3. An apparatus according to claim 1, characterized in that said component surfaces define means for receiving portions of said coupling means and in that said coupling means is a plate having portions received by said means for receiving.
 4. In an apparatus for simultaneously treating substantially plate-shaped workpieces with heat and pressure having a hearth having surface means for the reception of workpieces to be treated and cover means defining together with said surface means a treatment chamber, said cover means having a portion extending substantially in parallel to, but spaced apart from said surface means; heat generating means within said chamber; ram means in cooperating relation with said surface means for moving said surface means under pressure in a direction toward said portion of said cover means into said chamber to press the workpieces thereon against said cover means, the improvement comprising: a plurality of separate component surfaces comprising said surface means, a plurality of ram members comprising said ram means, each of said component surfaces being mounted in said hearth for independent movement by an associated one of said ram members, and said cover means including packing means, located above at least one of said component surfaces, for reducing the dimension of the treatment chamber in the direction of the movement of said surface means.
 5. An apparatus according to claim 4, characterized in that each of said component surfaces is larger than the bottom surface of each workpiece. 